Audio coding systems, such as Dolby AC-3 and MPEG-2 audio, permit the transmission of high-quality audio signals, including, in particular, the transmission of multi-channel sound. If the possible reproduction configurations are defined by "x,y", where x is the number of front channels and y is the number of surround channels, then, for example in the case of Dolby AC-3, the following reproduction configurations are possible: 3/2, 3/1, 2/2, 3/0, 2/1, 2/0, 1/0. In addition, a low-frequency channel can also be transmitted.
In order to enable such multi-channel sound reproduction, the transmitted audio data stream must first of all be decoded by a multi-channel audio decoder suitable for this purpose. However, if the device provided for reproduction contains merely a two-channel audio decoder, then multi-channel sound reproduction can be carried out only by using an external multi-channel audio decoder. The audio data are in this case output via a serial digital interface from the reproduction device to the multi-channel decoder. If the audio signals are intended to be output accompanying a video signal, such as, for example, during the playback of a film stored on a DVD, then a synchronization method is necessary in order to achieve lip synchronism between the picture and multi-channel sound reproduction.